Docker execution environment in Selenium Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Selenium test inside Docker container

Consider this Selenium Java test code running inside a Docker container with ChromeDriver. What will be the output printed to the console?

Selenium Java

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;

public class DockerSeleniumTest {
    public static void main(String[] args) {
        System.setProperty("webdriver.chrome.driver", "/usr/bin/chromedriver");
        WebDriver driver = new ChromeDriver();
        driver.get("https://example.com");
        String title = driver.getTitle();
        System.out.println(title);
        driver.quit();
    }
}

A Example Domain

B NoSuchSessionException

C SessionNotCreatedException

D WebDriverException: unknown error: cannot find Chrome binary

💡 Hint

Think about what the test does after opening the page inside Docker with ChromeDriver.

The test opens https://example.com inside the Docker container using ChromeDriver and prints the page title. Since the container has Chrome and ChromeDriver properly installed, the output is the page title 'Example Domain'.

❓ assertion

intermediate

Correct assertion for page title in Docker Selenium test

Which assertion correctly verifies the page title is 'Welcome' in a Selenium Java test running inside Docker?

Selenium Java

String actualTitle = driver.getTitle();

A assertFalse(actualTitle.equals("Welcome"));

B assertNull(actualTitle);

C assertTrue(actualTitle == "Welcome");

D assertEquals("Welcome", actualTitle);

💡 Hint

Use the correct JUnit assertion method for string equality.

assertEquals("Welcome", actualTitle) correctly compares the expected string with the actual title. Using '==' compares references, which is incorrect for strings.

❓ locator

advanced

Best locator strategy for dynamic element in Docker Selenium test

Inside a Docker Selenium test, which locator is best to find a button with changing id but fixed visible text 'Submit'?

A By.xpath("//button[text()='Submit']")

B By.cssSelector("button#submitBtn")

C By.id("submitBtn")

D By.name("submit")

💡 Hint

Choose a locator that relies on stable visible text rather than dynamic attributes.

Using XPath with the button's visible text is reliable when the id changes dynamically. Locators by id or name may fail if those attributes change.

🔧 Debug

advanced

Identify cause of WebDriver timeout in Docker Selenium test

A Selenium test running inside Docker fails with a timeout waiting for element located by By.id("login"). What is the most likely cause?

A The test code uses incorrect syntax for locating elements

B The Docker container lacks network access to load the page

C The element with id 'login' does not exist on the page loaded inside Docker

D The ChromeDriver version is incompatible with Chrome browser inside Docker

💡 Hint

Consider what happens if the element is not present on the page.

Timeout waiting for element usually means the element is not present or visible. Network or version issues cause different errors. Syntax errors cause compile or runtime exceptions.

❓ framework

expert

Best practice for parallel Selenium tests in Docker environment

Which approach is best to run multiple Selenium tests in parallel inside Docker containers to avoid session conflicts?

A Run all tests in a single Docker container sharing one ChromeDriver instance

B Use a Selenium Grid with multiple Docker containers each running a separate browser instance

C Run tests sequentially inside one Docker container to avoid conflicts

D Use a single WebDriver instance shared across all test threads inside Docker

💡 Hint

Think about isolation and scalability for parallel tests.

Selenium Grid with multiple containers allows isolated browser sessions for parallel tests. Sharing one instance causes conflicts. Sequential runs do not achieve parallelism.